Blade construction for use in slicing material webs

ABSTRACT

The present invention concerns a blade construction (10) for use in longitudinally cutting (in slicing) material webs, such as various paper and cardboard webs, films and recorder tapes, etc., with said cutter a material web being longitudinally parted into partial webs, the cutter consisting of a blade construction (10) comprising one or several blade pairs (11,12). On the edge (13) of a first blade (11), and similarly on the edge (15) of a second blade (12), has by grinding been produced a micro-rounding, and on the apex of the first blade (11) has been produced a bead (14). The radius (r) applied in micro-rounding is advantageously within 0.5-μm, and the dimension of the bead is advantageously within 0.1-1 mm.

This is a continuation of application Ser. No. 07/208,163 filed Jun. 16,1988 now abandoned.

The present invention concerns a blade construction for use inlongitudinally cutting, or slicing, material webs, such as various paperand cardboard webs, films, recorder tapes, etc., with said cutter amaterial web being parted longitudinally into partial webs, and thecutter consisting of a blade construction composed of one or severalblade pairs.

The cutting blades of this kind of cutter consist of blade pairs, andendeavours have been made to improve the service life of said cutters byusing circular blades made of a wear-resistant and hard but brittlematerial. The material of the blade edges may be e.g. ceramic, or a hardmetal.

The so-called shear-cutting method applied in longitudinal cuttingimplies that the cutter blades are pressed against each other with aforce which acts axially to the blades. Because of the toe-in of theblades, the blades are in contact at one point. The force that isapplied and the point contact cause a high stress concentration on theedges of the blades. When brittle blade materials are used, the stressconcentration easily exceeds the ultimate strength of the material, andsmall fractures result on the blade edges. Damaged blades are, ofcourse, unfit for use.

The object of the invention is to provide an improvement in the bladeconstruction of cutting blades used in longitudinal cutting. A moredetailed aim of the invention is to provide a blade constructionenabling the stress concentration on the blade edges to be reduced sothat no chipping of blade edges will occur.

The aims of the invention are achieved with a blade construction whichis mainly characterized in that on the edge of the first blade, andsimilarly on the edge of the second blade, has by grinding been produceda micro-rounding, and that on the apex of the first blade has beenproduced a bead. In the present context, the term bead is understood tomean a narrow cylinder produced by grinding on the apex of the blade.

The radius applied in the micro-rounding is advantageously within 0.5 to10 μm . The size of the bead is advantagoeusly within 0.1 to 1 mm.

In the blade construction of the invention, the ground micro-roundingand the bead reduce the stress concentration at the contact point tosuch a degree that the ultimate strength of the material will not beexceeded. The dimensions of the micro-rounding and the bead depend onthe blade force used and on the material to be sliced. When materialwebs are sliced with the blade construction of the invention, anexcellent cut is obtained for instance in paper. The most commonapplication of the blade construction of the invention is therefore theslicing of thin material webs in particular.

The invention is described in detail referring to an advantageousembodiment of the invention presented in the figures of the drawingattached, yet to which the invention is not meant to be exclusivelyconfined.

FIG. 1 presents, in sectional view, an advantageous embodiment of theblade construction of the invention, at the contact point of the blades.

FIG. 2 shows the upper blade and its geometry.

FIG. 3 shows the lower blade and its geometry.

In the embodiment of FIGS. 1-3, the blade construction of the inventionin general is indicated by reference numeral 10. In the presentembodiment, the blade constuction 10 consists of an upper blade 11 and alower blade 12. The hard metal part of the upper blade 11 is indicatedby reference numeral 11a and the hard metal part of the lower blade 12,by reference numeral 12a. The cutting edge of the upper blade 11 isindicated by reference numeral 13 and is defined between a surface 16and a bead 14, and the cutting edge of the lower blade 12 is indicatedby reference numeral 15 and is defined between two surfaces 17 and 18.In the present embodiment, the pair of blades is so disposed that theupper blade 11 is substantially conical. The clearing angle of the upperblade 11 is denoted with α, and the clearing angle of the lower blade issimilarly denoted with β.

The magnitude of the angle α is within 0°-5°, advantageously about 2°,and the magnitude of the angle β is within 0°-5°, advantageously about1°.

The blades 11 and 12 are circular blades. The central axis of the blade11 is indicated by A and that of the blade 12s by B.

As taught by the basic idea of the invention, the hard metal part 11a ofthe upper blade is micro-rounded at the edge 13, and similarly the hardmetal part 12a of the lower blade 12 is micro-rounded at the edge 15.The radius r of the micro-rounding applied is advantageously within0.5-10 μm. Furthermore, in the present embodiment the bead 14 isproduced on the hard metal part 11a of the upper blade 11, its dimensionadvantageously within 0.1-1 mm.

As shown in FIG. 1, the peripheral surface 19 of the upper blade 11 isconical and the peripheral surface 18 of the lower blade 12 iscylindrical. The bead 14 is defined by a generatrix that issubstantially parallel to the axis A, and extends between the cuttingedge 13 of the blade 11 and a second edge, which is defined between thebead and the conical peripheral surface 19 of the blade. The peripheralsurface 19 is at an acute angle to the surface 16. The peripheralsurface 18 of the blade 12 is defined by a generatrix that issubstantially parallel to the axis B. The peripheral surface 18 of thelower blade is substantially wider than the bead 14.

In the foregoing is presented only one advantageous embodiment of theinvention, and it is obvious to a person skilled in the art thatnumerous modifications thereof are feasible within the scope of theinventive idea stated in the claims following below.

I claim:
 1. A cutter for use in longitudinally cutting a material webinto partial webs, comprising at least one blade pair composed of afirst blade and a second blade, each having a cutting edge, the cuttingedges being in point contact and in shearing relationship and each beingmicro-rounded to a radius within the range from about 0.5 μm to about 10μm, and only the first blade having a bead adjacent its cutting edge. 2.A cutter according to claim 1, wherein the bead is defined between thecutting edge of the first blade and a second edge thereof, and the firstblade has a first surface that meets the bead at the cutting edge and asecond surface that meets the bead at said second edge, the firstsurface being at an angle in the range from about 85° to about 90° tothe bead.
 3. A cutter according to claim 2, wherein the first surface isat an angle of about 89° to the bead.
 4. A cutter according to claim 2,wherein the second blade has a first surface and a second surface thatmeet at the cutting edge of the second blade, the first surface being atan angle in the range from about 85° to about 90° to the second surface.5. A cutter according to claim 4, wherein the first surface of thesecond blade is at an angle of about 88° to the second surface thereof.6. A cutter according to claim 4, wherein the second surface of thesecond blade is defined by a generatrix perpendicular to the cuttingedge of the second blade, and the bead of the first blade is defined bya generatrix perpendicular to the cutting edge of the first blade, thetwo generatrices being substantially parallel.
 7. A cutter according toclaim 2, wherein the perpendicular distance between the cutting edge andthe second edge of the first blade is in the range from about 0.1 mm toabout 1 mm.
 8. A cutter according to claim 2, wherein the second surfaceof the first blade is at an acute angle to the first surface thereof. 9.A cutter according to claim 1, wherein the bead has a width in the rangefrom about 0.1 mm to about 1.0 mm and is defined between the cuttingedge of the first blade and a second edge thereof, and the first bladehas a first surface that meets the bead at the cutting edge at an anglein the range from about 85 degrees to about 90 degrees and a secondsurface that meets the bead at said second edge and is at an acute angleto the first surface of the first blade, and wherein the second bladehas a first surface and a second surface that meet at the cutting edgeof the second blade at an angle in the range from about 85 degrees toabout 90 degrees, and wherein the second surface of the second blade isdefined by a generatrix perpendicular to the cutting edge of the secondblade and the bead is defined by a generatrix perpendicular to thecutting edge of the first blade, the two generatrices beingsubstantially parallel and the second surface of the second blade beingsubstantially wider than the bead.
 10. A cutter according to claim 9,wherein the first surface of the first blade meets the bead at an angleof about 89 degrees and the first surface of the second blade meets thesecond surface thereof at an angle of about 88 degrees.
 11. A cutteraccording to claim 9, wherein the first surface of the first blade is ata first predetermined angle to the bead and the first surface of thesecond blade is at a second predetermined angle to the second surfacethereof, the second predetermined angle being about 1 degree smallerthan the first predetermined angle.
 12. A disk cutter for use inlongitudinally cutting a material web into partial webs, comprising atleast one blade pair composed of a first circular blade and a secondcircular blade rotatable about respective axes of rotation, each bladehaving a circular cutting edge, the cutting edges being in point contactand in shearing relationship and each being micro-rounded to a radiuswithin the range from about 0.5 μm to about 10 μm and only the firstblade having, adjacent its cutting edge, a bead that extendssubstantially parallel to the axis of rotation of the first blade.
 13. Acutter according to claim 12, wherein the bead is defined between thecutting edge of the first blade and a second edge thereof, and the firstblade has a first surface that meets the bead at the cutting edge and asecond surface that meets the bead at said second edge, the firstsurface being at an angle in the range from about 85° to about 90° tothe bead.
 14. A cutter according to claim 13, wherein the first surfaceis at an angle of about 89° to the bead.
 15. A cutter according to claim13, wherein the second blade has a first surface and a second surfacethat meet at the cutting edge of the second blade, the first surfacebeing at an angle in the range from about 85° to about 90° to the secondsurface.
 16. A cutter according to claim 15, wherein the first surfaceof the second blade is at an angle of about 88° to the second surfacethereof.
 17. A cutter according to claim 15, wherein the bead of thefirst blade is defined by a first generatrix perpendicular to thecutting edge of the first blade and the second surface of the secondblade is defined by a second generatrix perpendicular to the cuttingedge of the second blade, the first and second generatrices beingsubstantially parallel to the axes of rotation of the first and secondblades respectively.
 18. A cutter according to claim 13, wherein theperpendicular distance between the cutting edge and the second edge ofthe first blade is in the range from about 0.1 mm to about 1 mm.
 19. Acutter according to claim 13, wherein the second surface of the firstblade is at an acute angle to the first surface thereof.
 20. A cutteraccording to claim 13, wherein the first blade is conical and isdisposed above the second blade.
 21. A cutter according to claim 20,wherein the second blade is cyclindrical.
 22. A cutter according toclaim 12, wherein the bead has a width in the range from about 0.1 mm toabout 10 mm and is defined between the cutting edge of the first bladeand a second edge thereof, and the first blade has a first surface thatmeets the bead at the cutting edge at an angle in the range from about85 degrees to about 90 degrees and a second surface that meets the beadat said second edge and is at an acute angle to the first surface of thefirst blade, and wherein the second blade has a first surface and asecond surface that meet at the cutting edge of the second blade at anangle in the range from about 85 degrees to about 90 degrees, andwherein the bead is defined by a first generatrix perpendicular to thecutting edge of the first blade and the second surface of the secondblade is defined by a second generatrix perpendicular to the cuttingedge of the second blade, the first and second generatrices beingsubstantially parallel to the axis of rotation of the first and secondblades respectively and the second surface of the second blade beingsubstantially wider than the bead.
 23. A cutter according to claim 22,wherein the first surface of the first blade meets the bead at an angleof about 89 degrees and the first surface of the second blade meets thesecond surface thereof at an angle of about 88 degrees.
 24. A cutteraccording to claim 22, wherein the first surface of the first blade isat a first predetermined angle to the bead and the first surface of thesecond blade is at a second predetermined angle to the second surfacethereof, the second predetermined angle being about 1 degree smallerthan the first predetermined angle.